@article{NeillElsenbeerKruscheetal.2006,
  author    = {Neill, Christopher and Elsenbeer, Helmut and Krusche, Alex V. and Lehmann, Johannes and Markewitz, Daniel and Figueiredo, Ricardo de O.},
  title     = {Hydrological and biogeochemical processes in a changing Amazon : results from small watershed studies and the large-scale biosphere-atmosphere experiment},
  doi       = {10.1002/Hyp.6210},
  year      = {2006},
  abstract  = {The Amazon Basin is the world's largest tropical forest region and one where rapid human changes to land cover have the potential to cause significant changes to hydrological and biogeochemical processes. The Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA) is a multidisciplinary, multinational research program led by Brazil. The goal of LBA is to understand how the Amazon Basin functions as a regional entity in the earth system and how these functions are changing as a result of ongoing human activity. This compilation of nine papers focuses on a central LBA question in the area of nutrient dynamics and surface water chemistry-how do changes in land use alter fluxes of dissolved and particulate materials from uplands across riparian zones and down the channels of river corridors? These papers cover work conducted in small watersheds on a wide range of topics within the spirit and geographical focus area of LBA: water balance and runoff generation, nutrient transformations in riparian zones and stream channels, carbon fluxes in water moving from land to water and the influence of soils on flowpath structure and stream chemistry. Important new insights can be gained from these and other studies. Forest clearing for pastures results in a decrease in soil hydraulic conductivity that forces water into surficial flowpaths throughout most of the rainy season across wide regions of the Amazon. Riparian zones along small forest streams appear to be very effective in removing nitrate arriving from the uplands, while forest streams take up nitrate at very low rates, allowing them to travel downstream for long distances. Although substantial, the contribution of dissolved organic C (DOC) to the carbon flux from forests to streams appears to be lower than the flux of dissolved inorganic C that is subsequently outgassed as CO2. Remaining key challenges within LBA will be to synthesize existing data sets on river networks, soils, climate, land use and planned infrastructure for the Amazon to develop models capable of predicting hydrologic and biogeochemical fluxes at a variety of scales relevant to the development of strategies for sustainable management of the Amazon's remarkable forest, soil and freshwater resources.},
  language  = {en}
}
@article{NeillChavesBiggsetal.2011,
  author    = {Neill, Christopher and Chaves, Joaqu{\´i}n E. and Biggs, Trent and Deegan, Linda A. and Elsenbeer, Helmut and Figueiredo, Ricardo O. and Germer, Sonja and Johnson, Mark S. and Lehmann, Johannes and Markewitz, Daniel and Piccolo, Marisa C.},
  title     = {Runoff sources and land cover change in the Amazon an end-member mixing analysis from small watersheds},
  series = {Biogeochemistry},
  volume    = {105},
  journal   = {Biogeochemistry},
  number    = {1-3},
  publisher = {Springer},
  address   = {Dordrecht},
  issn      = {0168-2563},
  doi       = {10.1007/s10533-011-9597-8},
  pages     = {7 -- 18},
  year      = {2011},
  abstract  = {The flowpaths by which water moves from watersheds to streams has important consequences for the runoff dynamics and biogeochemistry of surface waters in the Amazon Basin. The clearing of Amazon forest to cattle pasture has the potential to change runoff sources to streams by shifting runoff to more surficial flow pathways. We applied end-member mixing analysis (EMMA) to 10 small watersheds throughout the Amazon in which solute composition of streamwater and groundwater, overland flow, soil solution, throughfall and rainwater were measured, largely as part of the Large-Scale Biosphere-Atmosphere Experiment in Amazonia. We found a range in the extent to which streamwater samples fell within the mixing space determined by potential flowpath end-members, suggesting that some water sources to streams were not sampled. The contribution of overland flow as a source of stream flow was greater in pasture watersheds than in forest watersheds of comparable size. Increases in overland flow contribution to pasture streams ranged in some cases from 0\% in forest to 27-28\% in pasture and were broadly consistent with results from hydrometric sampling of Amazon forest and pasture watersheds that indicate 17- to 18-fold increase in the overland flow contribution to stream flow in pastures. In forest, overland flow was an important contribution to stream flow (45-57\%) in ephemeral streams where flows were dominated by stormflow. Overland flow contribution to stream flow decreased in importance with increasing watershed area, from 21 to 57\% in forest and 60-89\% in pasture watersheds of less than 10 ha to 0\% in forest and 27-28\% in pastures in watersheds greater than 100 ha. Soil solution contributions to stream flow were similar across watershed area and groundwater inputs generally increased in proportion to decreases in overland flow. Application of EMMA across multiple watersheds indicated patterns across gradients of stream size and land cover that were consistent with patterns determined by detailed hydrometric sampling.},
  language  = {en}
}